Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2005
Publication Date: 7/16/2005
Citation: Chappell, A.S., Bilyeu, K.D. 2005. A high-throughput screen for low phytic acid soybeans [abstract]. American Society of Plant Biologists Annual Meeting.
Technical Abstract: Inositol hexakisphosphate, or phytic acid, is a phosphorous storage compound widely utilized in plant seeds, including crop plant seeds such as soybeans. Monogastric livestock lack sufficient phytase activity to metabolize the phytic acid present in soybean feed, leading to inadequate phosphorous uptake. In addition, phytic acid strongly binds essential minerals such as zinc, calcium and iron, resulting in decreased bioavailability of several additional minerals. These antinutritional factors of phytic acid can be further extended to human health as phytic acid is considered to be the most important antinutritional factor contributing to the iron deficiency suffered by over 2 billion people worldwide. These antinutritional properties make the development and characterization of low phytic acid soybean lines a high priority in agricultural research. To this end, we are using a reverse genetics approach to identify mutations in known phytic acid biosynthesis genes. Although the exact biochemical pathway for phytic acid biosynthesis in soybean is not known, several key enzymes have been identified in various plant species. One such enzyme, inositol trisphosphate kinase (Itpk), has been identified in several plants including Arabidopsis and maize. We have identified three soybean ITPK genes based on homology to the Arabidopsis and maize genes. Using quantitative real-time PCR, we found that one of the three ITPK genes (ITPK3) is highly expressed in developing seeds. This gene is now the subject of TILLING (Targeting Induced Local Lesions IN Genomes), a high-throughput molecular assay used to detect mutations in target genes from a large set of mutated individuals.